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The effect of two-step aging treatment on the fatigue behavior of welded AA 7020 Al. alloy was investigated. For fatigue tests to be carried out in atmospheric and seawater environments, a plane bending tester at a stress ratio of R = 0 was used. Experiments in the control group were carried out with unwelded specimens at a strain rate of R = −1 in air. The gradual heat treatment, two-step aging, significantly improved the fatigue and corrosion fatigue behavior of welded AA 7020 alloys. Unwelded specimens showed better fatigue properties than the welded ones. In the experiments in the seawater environment, pitting, and exfoliation corrosion occurred on the surfaces. It was determined that the corrosion pits reduce the fatigue life of welded and unwelded specimens. It was also observed that the corrosion sensitivity of the welded specimens increased in the heat affected zone and resulted in corrosion fatigue cracking.

Bu çalışmanın amacı, dental implant malzemesi olarak kullanılan Ti6Al4V alaşımının yüzeyine PVD (Magnetron Sputtering) yöntemi ile biriktirilen gümüş tabakasının korozyon davranışını ve antimikrobiyal etkisini belirlemektir. Kaplamalar, aynı kaplama koşulları altında farklı biriktirme süreleri kullanılarak elde edilmiştir. Kaplamaların kesit morfolojileri ise taramalı elektron mikroskobu (SEM) kullanılarak tespit edilmiştir. Kaplamaların fazları X-ışını difraksiyonu (XRD) kullanılarak tespit edilmiştir. PVD yöntemi ile kaplanmış ve işlemsiz Ti-6Al-4V numunelerin üzerinde korozyon deneyleri Kokubo'nun simüle edilmiş vücut sıvısı (SBF) pH 7.4 ve 36.5 °C çözeltisi içinde ve normal atmosfer şartlarında gerçekleştirilmiştir. Buna ek olarak, In vitro anti-bakteriyel etkinlik deneylerinde numunelerin yüzeylerine E. coli (Escherichia coli) ve S. aureus (Staphylococcus aureus) mikroorganizmaları sürülerek kaplamanın antibakteriyel özelliği araştırılmıştır. Antibakteriyel özelliklerini ölçmek için ise plaka sayma yöntemi kullanılmıştır. XRD sonuçlarına göre numunelerin yüzeylerindeki kaplama tabakaların homojenliği, SEM analiziyle elde edilen kesit morfolojileri ile de desteklenmiştir. Potansiyodinamik polarizasyon test sonuçları, gümüş kaplamadan sonra korozyon direncinin arttığını göstermektedir. In vitro anti-bakteriyel etkinlik deneyleri sonucunda, PVD ile kaplanmış numunelerde E. Coli ve S.Aureus mikroorganizmalarının tutunumu, kaplanmamış numuneye göre daha az çıkması, kaplamanın anti-bakteriyellik yönünden uygun olduğunu göstermiştir.

The basic aim of this in vitro study was to investigate the effects of different silver deposition times on the two-body wear, antibacterial and cytotoxicity properties of silver ions on Ti15Mo alloy. The direct current (DC) magnetron sputtering technique was used to create silver films at different times (30, 45 and 60 minutes); the experimental setup was predetermined. The phase structures, cross-sectional morphology, surface roughness, two-body wear behavior, antibacterial and cytotoxicity properties of all specimens were researched in detail. The surfaces of all films showed a homogeneous distribution. It was observed that silver films enhanced the two-body wear resistance of Ti15Mo alloys. Furthermore, significant correlations were discovered between hardness, surface roughness and wear volume loss. Compared to Ti15Mo alloys, the antibacterial and cytotoxicity test results showed that silver films deposited 30 and 45 min had superior antibacterial and biocompatibility properties.

The aim of this in-vitro study was to evaluate the influence of Ag[Formula: see text]-ion-coated conditions on the corrosion, tribocorrosion and antibacterial properties of Ti15Mo alloy. The mean wear volume losses of all test specimens after tribocorrosion test procedures were determined using a noncontact 3D profilometer. The specimens’ hardness, roughness values and microstructures were measured using the microhardness tester, surface profilometer, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The mean wear volume loss of 30-min Ag[Formula: see text]-ion-coated Ti15Mo alloy was lower than the other specimens. In this study, correlations between the hardness, surface roughness and wear volume loss were found to be significant. The PVD coating process enhanced the antibacterial activity of Ti15Mo alloy owing mainly to the formation of silver film on the substrates.

The effect of two-step aging treatment on the fatigue behavior of welded AA 7020 Al. alloy was investigated. For fatigue tests to be carried out in atmospheric and seawater environments, a plane bending tester at a stress ratio of R=0 was used. Experiments in the control group were carried out with non-welded specimens at a strain rate of R= -1 in air. The gradual heat treatment (two step aging, TSA) significantly improved the fatigue and corrosion fatigue behavior of welded AA 7020 alloys. Unwelded specimens showed better fatigue properties than welded ones. In experiments in a seawater environment, pitting and exfoliation corrosion occurred on the surface. It was determined that the corrosion pits reduce the fatigue life of welded and unwelded samples. It was also observed that the corrosion sensitivity of the welded specimens increased in the heat affected zone (HAZ) and corrosion fatigue cracking occurred in these zones.

Background: The purpose of this work is to evaluation of contact-wear behavior of lithium disilicate glass ceramic materials under in vitro chewing tests. Methods: Eight specimens of each ceramic materials were exposed contact-wear tests using a computer-controlled chewing simulator (1.2 Hz 50 N bite force loads, 120.000 mechanical cycles, constantly 37 °C temperature immersed in distill water. Al2O3 balls of 6 mm in diameter were used for each chewing test. The mean volume loss of all ceramic specimens after the contact-wear tests was determined with use 3D profilometer. In addition to a random specimen was selected from each test group and scanning electron microscopy (SEM) images were taken for analysis of wear tracks. Results: As a result, the ceramic materials tested in this study showed similar wear behaviors after 120.000 chewing tests. Conclusions: However, it was observed that more particles were carried on the wear surface and occurred micro cracks of the IPS e.max ceramic material. These micro cracks can be the continuation of cracks that occur subsurface of ceramic material.

Background: The thermal changes in environments that composite materials are exposed to has a great effect on fatigue and wear behavior. Aim: Micro-cracks and interfacial deformations occur in the composite material structure because of heating and cooling environments occurring on material surfaces. Considering the environment to which bio-composite materials used in the human body are exposed, it is inevitable that they are exposed to a thermal change cycle environment. Material and Method: In this study, the mechanical behaviors of Silorane, X-Trafil and Valux-Plus bio-composite materials were examined after being exposed to thermal cycles in an artificial mouth environment in the temperature range of minimum 5 °C and maximum 65 °C. Micro-tensile strengths of bio-composite materials after thermal cycle test procedures were determined using a universal micro tensile tester device. In addition, microstructural analyzes of bio-composite materials were evaluated using scanning electron microscopy (SEM). Results: Within the scope of the data obtained as a result of this study, it was concluded that the thermal changes in environments significantly affects the micro-shrinkage behavior of bio-composite materials. Conclusion: The behavior of the matrix structure of the composite material significantly affected the formation of micro cracks.

This study investigated the damage mechanism occurring in metallic materials working under repeated impact loads. AISI 316L stainless steel was used as the test material. In order to reduce the impact wear (IW) damage without disturbing the structure of the material, a ball burnishing (BB) process was applied to the workpiece surface. IW tests were carried out in air at ambient temperature and a frequency of 5 Hz under a 560 N (0.12 J) load. This study also investigated the effects of three different cycles on the wear mechanism. As a result of the experiments, the amount of deformation and the volume loss on the surface increased in parallel with the number of impacts. Strain hardening occurred and the surface hardness increased. The IW process affected the surface region to a depth of 360 μm. According to the metallographic observations, the wear mechanism occurred in the form of delamination and flake like spalling. The BB process reduced IW induced volume loss between 62% to 53%.

Purpose The purpose of this study is to describe the environmentally assisted cracking (EAC) of AISI 316L stainless steel as bare and coated cases in several corrosion environments. The main purpose of this study is to extend the lifespan of 316L material under corrosive fatigue in sodium chloride environments. Design/methodology/approach Fatigue tests carried out by using a Schenk type plane bending fatigue machine made by Tokyokoki Co. A scanning electron microscope (SEM) was used to observe the fracture surfaces and tested specimen surfaces. The micro-Vickers hardness of specimens was measured by using a PC-controlled Buehler–Omnimet tester. Findings Under reciprocating bending condition (R = −1) the behavior of 316L SS bare samples and 316L SS coated with Al-5%Mg samples were investigated comparatively at room temperature in ambient air and in several corrosion solutions. The results obtained from the data showed that Al-5Mg coating procedure significantly stabilized the 316L SS even in the most aggressive environment 5 per cent NaCl solution as compared with bare samples. Originality/value Al-5Mg coating showed a stable structure under the corrosion liquids used in the experiments. The coating material served as a stable barrier between the base material and the corrosion fluid, thus ensuring a tightness even in long-term tests below the endurance limit.

To determine the effect of different temperature on the wear amounts of dental composite material prepared in Pre-heating Temperature (PTG,60 degrees C) and Room Temperature (RTG,23 degrees C). To increase the Degree of conversion (%DC) in material by pre-heating process, and to investigate the effects of the employed method on the amount of wear. To evaluate the effect of %DC on the material's surface roughness.To evaluate the effect of thermal cycling on the material's surface roughness. Valux (TM) Plus, x-trafil and Charisma (R) Classic materials were polymerised in two groups: RTG and PTG. The mechanical loadings were applied simultaneously with different In vitro Chewing Environment Temperature (ICET). To perform the thermal cycle (ICET = 5/55 degrees C), 20,000 thermal cycles were applied simultaneously with 500,000 mechanical loading. Amounts of wear, hardness, %DC, and surface roughness were evaluated statistically by ANOVA. Amount of wear rate, and loss of filler particles at the wear zones were changed in different ICET conditions. Pre-heating process caused increase in %DC, surface roughness, and hardness value of all materials. The increase of %DC increased wear resistance in ICET = 5 degrees C, 35 degrees C, and 55 degrees C for x-trafil and Charisma (R) Classic. Moreover, the same pattern was recorded for the ICET = 5 degrees C for Valux (TM) Plus material. In Valux (TM) Plus, x-trafil and Charisma (R) Classic materials the maximum wear occurred in the RTG group at the ICET = 5 degrees C. Pre-heating and thermal cycling processes caused increase of the surface roughness values. For all materials the pre-heating process caused decrease of wear resistance in the ICET = 5/55 degrees C.

Corrosion fatigue (CF) behavior of AISI 316L was investigated in a 3 pct NaCl aqueous solution at an R = − 1 stress ratio and a frequency of 60 Hz at room temperature. The test scale specimen was 7 cm2. The passive (0 mVRef), pitting (120 mVRef), and cathodic (− 1400 mVRef) polarization potentials were statically applied and recorded during CF tests until the samples were broken. The shaft material surface was treated with a ball burnishing (BB) process. By the results, the fatigue behavior of AISI 316L was affected by polarization potential and surface treatment. Under 0 mV potential charged tests for 5 × 105 cycles, BB treatment raised the CF strength of the shaft material from about 448 to 702 MPa with a percent 57 increase. Fractographic observations revealed that corrosion pits occurred during the experiments where anodic potential was applied and that transgranular surface fractures occurred in all cases.

The purpose of the present study was to investigate two and three-body wear resistance and hardness of eighth kinds of modern bulk-fill and resin-based composite materials — Grandio, Estelite Flow, Filtek bulk-fill, Charisma, Clearfil, Ultimate, Quadrant, and G-aenial. All samples were kept in distilled water for one week, and their Vickers hardness was determined before two- and three-body wear tests. The mean volume loss of all specimens after the wear tests was determined by the 3D profilometry. In addition, a random specimen was selected from each test group and scanning electron microscope images were taken for an analysis of wear tracks. The surface morphology of the Clearfil and Ultimate composite materials was damaged severely, whereas Grandio and Charisma had a very smooth surface after two-body wear tests. The lowest mean volume loss was measured in micro-fill Grandio two-body and three-body wear tests. The Filtek bulk-fill and resinbased composites showed similar two- and three-body wear behavior. For the composite materials considered, correlations between the filler volume loss, Vickers hardness, and two- and three-body wear resistances were found to be insignificant.